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[flang] Treat hlfir.associate as Allocate for FIR alias analysis. (#139004)

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Early HLFIR optimizations may experience problems with values
produced by hlfir.associate. In most cases this is a unique
local memory allocation, but it can also reuse some other
hlfir.expr memory sometimes. It seems to be safe to assume
unique allocation for trivial types, since we always
allocate new memory for them.
This commit is contained in:
Slava Zakharin 2025-05-12 18:34:12 -07:00 committed by GitHub
parent 2d12d31f44
commit ee47aea435
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7
flang/include/flang/Optimizer/HLFIR/HLFIROps.td
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@ -759,6 +759,13 @@ def hlfir_AssociateOp : hlfir_Op<"associate", [AttrSizedOperandSegments,
For expressions, this operation is an incentive to re-use the expression
storage, if any, after the bufferization pass when possible (if the
expression is not used afterwards).
For aliasing purposes, hlfir.associate with the source being
a trivial FIR value is considered to be a unique allocation
that does not alias with anything else. For non-trivial cases
it may be a unique allocation or an alias for the source expression
storage, so FIR alias analysis will look through it for finding
the source.
}];
let arguments = (ins

14
flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
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@ -540,6 +540,20 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v,
v = op.getVar();
defOp = v.getDefiningOp();
})
.Case<hlfir::AssociateOp>([&](auto op) {
mlir::Value source = op.getSource();
if (fir::isa_trivial(source.getType())) {
// Trivial values will always use distinct temp memory,
// so we can classify this as Allocate and stop.
type = SourceKind::Allocate;
breakFromLoop = true;
} else {
// AssociateOp may reuse the expression storage,
// so we have to trace further.
v = source;
defOp = v.getDefiningOp();
}
})
.Case<fir::AllocaOp, fir::AllocMemOp>([&](auto op) {
// Unique memory allocation.
type = SourceKind::Allocate;

30
flang/test/HLFIR/opt-bufferization-eval_in_mem-with-associate.fir Normal file
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@ -0,0 +1,30 @@
// RUN: fir-opt --opt-bufferization %s | FileCheck %s
// Verify that hlfir.eval_in_mem uses the LHS array instead
// of allocating a temporary.
func.func @_QPtest() {
%cst = arith.constant 1.000000e+00 : f32
%c10 = arith.constant 10 : index
%0 = fir.dummy_scope : !fir.dscope
%1 = fir.alloca !fir.array<10xf32> {bindc_name = "x", uniq_name = "_QFtestEx"}
%2 = fir.shape %c10 : (index) -> !fir.shape<1>
%3:2 = hlfir.declare %1(%2) {uniq_name = "_QFtestEx"} : (!fir.ref<!fir.array<10xf32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xf32>>, !fir.ref<!fir.array<10xf32>>)
%4:3 = hlfir.associate %cst {adapt.valuebyref} : (f32) -> (!fir.ref<f32>, !fir.ref<f32>, i1)
%5 = hlfir.eval_in_mem shape %2 : (!fir.shape<1>) -> !hlfir.expr<10xf32> {
^bb0(%arg0: !fir.ref<!fir.array<10xf32>>):
%6 = fir.call @_QParray_func(%4#0) fastmath<contract> : (!fir.ref<f32>) -> !fir.array<10xf32>
fir.save_result %6 to %arg0(%2) : !fir.array<10xf32>, !fir.ref<!fir.array<10xf32>>, !fir.shape<1>
}
hlfir.assign %5 to %3#0 : !hlfir.expr<10xf32>, !fir.ref<!fir.array<10xf32>>
hlfir.end_associate %4#1, %4#2 : !fir.ref<f32>, i1
hlfir.destroy %5 : !hlfir.expr<10xf32>
return
}
// CHECK-LABEL: func.func @_QPtest() {
// CHECK: %[[VAL_0:.*]] = arith.constant 1.000000e+00 : f32
// CHECK: %[[VAL_3:.*]] = fir.alloca !fir.array<10xf32> {bindc_name = "x", uniq_name = "_QFtestEx"}
// CHECK: %[[VAL_5:.*]]:2 = hlfir.declare %[[VAL_3]](%[[VAL_4:.*]]) {uniq_name = "_QFtestEx"} : (!fir.ref<!fir.array<10xf32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xf32>>, !fir.ref<!fir.array<10xf32>>)
// CHECK: %[[VAL_6:.*]]:3 = hlfir.associate %[[VAL_0]] {adapt.valuebyref} : (f32) -> (!fir.ref<f32>, !fir.ref<f32>, i1)
// CHECK: %[[VAL_7:.*]] = fir.call @_QParray_func(%[[VAL_6]]#0) fastmath<contract> : (!fir.ref<f32>) -> !fir.array<10xf32>
// CHECK: fir.save_result %[[VAL_7]] to %[[VAL_5]]#0(%[[VAL_4]]) : !fir.array<10xf32>, !fir.ref<!fir.array<10xf32>>, !fir.shape<1>
// CHECK: hlfir.end_associate %[[VAL_6]]#1, %[[VAL_6]]#2 : !fir.ref<f32>, i1